This application is designed to investigate the role of the inflammatory mediator, CAP37, in ocular inflammation. CAP37 was recently identified in the eye in response to bacterial infection. Surprisingly, its localization was not confined to the neutrophil (PMN), where it is known to be constitutively expressed, but it was also found induced in corneal epithelial cells, and vascular endothelial cells of the limbal and ciliary vessels. There are many inflammatory-associated biological activities regulated by CAP37 that confer on this molecule a role in innate host defense against invading pathogens. CAP37 is a potent antibiotic, promotes monocyte chemotaxis, and has immunomodulatory effects on host cells including corneal epithelial cells. The induction of a host defense molecule in the outermost layers of the eye and in the vascular endothelium in response to infection, suggests that it could play a key role in regulating inflammation and healing in the cornea and in the long term form the basis for developing new therapeutics for certain eye infections. It is our hypothesis that CAP37, either released by PMNs or induced in corneal epithelial cells at the site of infection, plays a pivotal role in the inflammatory response of the cornea to infection. We hypothesize that it accomplishes this through a novel, dual mechanism of action based on its antibiotic/anti-inflammatory and immunomodulatory properties. Aim 1: To test the hypothesis that the regulation of proliferation, chemotaxis, and adhesion of corneal epithelial cells in ocular inflammation is dependent on CAP37 and is mediated through the intracellular signaling molecule protein kinase C, we will use techniques that include immunohistochemistry, pharmacological inhibitors, and RNA interference. Aim 2: To test the hypothesis that CAP37 is a biologically relevant mediator in host defense in the eye, we will measure the induction and identity of inflammatory cells, mediators, cytokines, and adhesion molecules in response to the administration of CAP37, its bioactive peptides, and neutralizing antibodies into the corneal stroma. Flow cytometry, ELISA, immunohistochemistry, and RT-PCR will be used to analyze data. Aim 3: To test the hypothesis that the anti-inflammatory and immunomodulatory properties of CAP37 are important for host defense in ocular infection we will use CAP37 and its bioactive peptides in a murine model of Pseudomonas aeruginosa keratitis to determine in vivo efficacy. Relevance to public health: Once corneal integrity is breached, prompt treatment with antibiotics is required to halt the development of infection and harmful sequelae such as ulceration, perforation, scarring, and loss of vision. Unfortunately, the antibiotics currently available for ophthalmic use have serious limitations. We believe our findings will help develop new therapies for treating wounds and infections of the eye based on the biological molecule CAP37 and its bioactive peptides.